Here's a wonderful and rather unusual piece of calculating history. This
is a Wang Model 360SE Calculating System.

Wang Laboratories (Tewksbury, Massachusetts), founded in 1951 by
Dr. An Wang as a one-man electronics company, became famous for revolutionizing
electronic calculators by providing higher level math functions which
previously were only available on very expensive computer systems.
Dr. Wang invented a combination of digital electronic circuits (patented
in 1968) that used a method called "factor combining" to generate the
base e logarithm of any number. The properties of logarithms make
it much easier to perform functions such as square root, raising numbers
to powers, as well as dramatically simplifying multiplication and division
via electronic circuits. Using any other method to perform such calculations
would have taken far too many components, resulting in a larger and more
expensive machine. The factor combining method of generating logarithms
was particularly suited for implemention in electronic circuitry because
the algorithm uses only a table of constants, addition, subtraction, and
multiplication and division by 10 (which is easily accomplished by simple
shifting).

The 300-series of calculators were the second line of electronic calculators
introduced by Wang. The first programmable electronic calculator marketed
by Wang Laboratories was the LOCI-2,
(LOCI, pronounced "Low-Sigh", is an acronym for LOgarithmic
Computing Instrument) introduced in January of 1965. The
LOCI-2 was rather large and clunky, and really not very intuitive in terms
of its operation, making it more useful to scientists and mathematicians
rather than business people.
The LOCI-2's introductory price of $6500 was significantly higher than other
calculators (electronic and electromechanical) of the time, but the machine
could perform complex math operations with a few keystrokes, as well as
offering optional programmability via punched cards,
which gave it an advantage over other electronic calculators
of the time. The LOCI-2 calculator used Dr. Wang's logarithmic calculation
circuit, and proved to an eager marketplace that the electronic calculator
had a place in engineering and scientific calculations. The LOCI-2's
marketplace lifetime was short, though, due in part to its complex and
non-intuitive operation, and also due to the introduction of the Wang 300-series
calculators, which were easier to use, smaller, and less expensive.

The Model/Serial Number Tag and In-Service Date Sticker

The 300-series machines were first publically shown in October of 1965, and
received a great deal of interest from a market hungry for (comparatively)
low-cost number crunching power. The response was tremendous, giving Wang
the confidence to make the investment and begin mass production of the
calculators. The first machines went into production in
March of 1966. The initial introduction consisted of three models, the
300E, 310E, and 320E. The electronics package on all of these units
was virtually identical electronically, with the 320E containing a full
compliment of cards, the 310E missing one card, and the 300E missing two
cards. Each model of electronics package had a corresponding keyboard
unit that was plugged into it. The Model 300E calculator used the 300K
keyboard, which provided no access to the scientific functions. The Model 310E
calculator came with the 310K keyboard, which added single-key squaring and
square root functions, and the Model 320E calculator came with the 320K
keyboard, which added natural logarithm and antilogarithm to the functions
of the 310.

To some degree, the Model 300, 310 and 320 calculators were clever marketing
ploy. The only real difference between a Model 300 system and a 320 (which
cost over $400 more than the 300) was the addition of two simple circuit
boards populated with diodes and resistors in the electronics package,
and changes to the keyboard/display unit including
the addition of four microswitches; four keycap assemblies; and a keyboard
bezel punched with four additional holes for the scientific function keys.
These changes certainly cost Wang Laboratories much less than the $400
difference. However, in terms of functionality, the functions provided
on the Model 320 calculator were probably worth much more to scientists,
mathematicians, and engineers who found the instant answers to more complex
math operations a godsend. The same differences existed in the simultaneous
calculators, (the 300SE, 310SE, and 320SE, as well as the 210SE and 250SE),
with the only differences in the electronics packages being the removal
of one or two diode logic boards.

By early 1967, other units, including the "SE" (Simultaneous)
calculators, were added to the line. Production of the SE (Simultaneous)
models (300SE, 310SE, and 320SE) began in February of 1967, with the 360SE
coming out shortly afterward.

After the 300-series calculators
were on the market for a while, it became apparent to Wang that the
machines had a problem that made them unsuitable for a sizable chunk of
market share. The machines, while truly stunning in their applicability
for scientific and engineering functions, were a bit tedious to use in
financial realms. Finance folks like to have answers presented in
dollars and cents. The floating decimal system used by the 300-series
calculators was perfect for scientific and engineering functions, as the
decimal was always positioned correctly for maximum accuracy.
In the case of financial calculations, only two digits behind the
decimal point are really needed, with appropriate round-off occurring
based on the third digit behind the decimal point. Re-engineering
the 300-series architecture to switch to a fixed decimal point mode
would have been expensive, requiring an almost new design. Rather than
do this, addition of a rather simple logic board created a new series
called the 200-series, that provided an automatic round-off at the
third digit behind the decimal point. So, 2 ÷ 3 on a 300-series
calculator would give 0.666666667, while on a 200-series machine, would
provide 0.670000000. The decimal was still floating, but since there
was never any result beyond the second digit behind the decimal point,
the 200-series was perceived as more suitable for financial and business
use. Two machines were introduced in the 200-series, sometime
in late 1967. The 210SE, and the 250SE were produced specifically
to meet the needs of business and financial users. The 210SE used a Model
320SE electronics package with the addition
of the special "round-off" board. The 250SE used the 360SE
electronics package with the round-off board, providing the additional
memory capability of the 360 to users who needed it.

The 360SE electronics package
exhibited here was sold in May of 1969, based on the in-service date sticker.
A Wang 300-series system consists of an electronics package (Wang's
term), and keyboard/display unit(s) that plug into the electronics
package. The electronics package contains all of the
brains of the calculator system, and the keyboard/display units provide
the operator interface to the calculator.

The 'guts' of the 360SE Electronics Package

Core Plane Card in 360SE Electronics Package

Hand-Wired Backplane of 360SE Electronics Package

The 360SE electronics package consists of 32
printed-circuit cards (Wang called the circuit cards "LogiBlocs") that plug
into edge-card connectors. The backplane is hand-wired, using individual
wires connected to square pin tails on the edge connector sockets using a unique
clip system. Some of the later (early
1970's) 300-series non-simultaneous electronics packages that I have seen
use a printed-circuit backplane. It may be that
the simultaneous versions of the electronics package always used a hand-wired
backplane (because their complexity may have precluded the use of a printed-
circuit backplane), and the less-complex single-user electronics packages
may have started out using a hand-wired backplane, later switching to
the printed-circuit backplane once the printed circuit technology was
perfected. I have not yet come across a simultaneous electronics package
that did not have a wired backplane, while I have seen both wired and
circuit board backplanes in non-simultaneous 300-series electronics packages.

If you have a Wang 300-series electronics package, I would very much
appreciate it if you could send me information on the model number, serial
number, and the type of backplane that the electronics package has.

The LogiBlocs have components and traces on one side, and traces only on
the back side, with jumper wires providing connections between sides of the
board. In all of the general circuitry of the machine, standardized
components are used. Most of the transistors are of the same type (made
by RCA), with exceptions in areas such as the timing and control circuitry,
core stack drivers and amplifiers, and display driving circuits. The logic
appears to be fairly generic diode-resistor/transistor logic for gating
functions, and basic types of flip-flop circuits for registers and counters.
The three main registers of the calculator (two adder accumulators and
the logarithm accumulator) are stored within the core memory subsystem.
The core subsystem also contains the store/recall memory registers in
models that offer this feature. In the 360SE, a single circuit card contains
four core arrays and steering diodes. Another couple of boards have
the timing/sequencing, driver, and sense amplifier circuitry to control the
core array.

Special Wang "T" Connector to Allow Two Keyboard/Display Units to be Connected to One Calculator Port

There are two types of 300-series electronics packages; the E models (see
the exhibit on the Wang 360E for an example),
and the SE models. The E-version of the electronics packages provide one
connector for plugging in a keyboard. Wang provided special
connectors (see photo) to allow multiple keyboard/display units to
be connected to an E-series electronics package, but only one keyboard/display
unit could be used at a time.

The SE (with the "S" standing for Simultaneous) electronics packages
have four connectors for plugging in keyboard/display units. All four
keyboard/display units operate at once as independent calculators,
with the logic providing a round-robin timesharing of the computing
electronics amongst the keyboard/display units.

The base Wang-300-series system was the Model 300.
This entry-level system came with the 300K keyboard/display unit,
and provided access only to add, subtract, multiply, and divide functions.

The 300K Keyboard Layout (click image for more details)

The Model 310 system provided the model 310K keyboard/display unit, which
added access to one-key squaring and square root functions.

The 310K Keyboard Layout (click image for more details)

The Model 320 system added to the 310's functions with addition of
ex and Loge(x) functions to the
320K keyboard/display unit.

The 320K Keyboard Layout (click image for more details)

The Model 360 system came with the 360K keyboard/display unit,
that added access to four store/recall memory registers in addition to the
functions provided by the 320K keyboard/display unit. In March of 1969,
an additional model was added to the 300-series, the Model
362E electronics
package, wth the 362K keyboard/display unit. The 362E provided more memory,
and a different scheme for addressing the memory storage registers, providing
access to 12 'full' (14-digit w/sign & decimal location) memory registers, or
24 'half' (6-digit w/sign & decimal
location) memory registers. Functions were provided to store or recall to
a 'full' register, or to each 'half' of a specified register, along with
the ability to add or subtract a value from a full memory register.
Memory registers in the 362 were addressed by pressing a digit from
zero through nine (to address memory registers 0 through 9) after the memory
command key, or "CLEAR DISPLAY" (for memory register 10), or "CHANGE SIGN"
(for memory register 11).

The 360K and 362K Keyboard Layouts

Optionally, there were versions of the 320K, 360K or 362K keyboard unit
available that provided built-in programs for trigonometric functions.
There were two different versions of the 320/360/362 trig keyboards, the
KT and the KR. The KT model keyboards (320KT, 360KT and 362KT) use
degrees for the trig functions, while the KR versions use radians.

Model 360KT Trig Keyboard

The KT and KR keyboard/display units are unique in that they include
a transistorized sequencing unit built into the keyboard unit that provides
ROM-based 'programs' for calculating sin, cos, sin-1, and
tan-1 functions. The keys for these functions are at the
upper-left of the keyboard as pictured above.

Trig function sequencer board

This photo shows the sequencing board inside a 360KT 'trig' keyboard. This
sequencer provides a series of 'virtual keypresses' to the electronics package
to perform the trigonometric functions. There's a small slide switch on the
right center of the sequencer board that is marked "Cont/Step". Immediately to
its right is a micro-switch that, when activated, will perform one 'program'
step of a trig operation when the slide switch is
in the 'Step' position. Diode-ROM arrays on two plug-in cards are mounted
on the back of the sequencer board which contain the keypress sequences for the
trigonometric functions. The difference between the KT and KR trig keyboards
is the plug-in ROM arrays which make up the programs for the
trig functions.

Diode-ROM Arrays Containing Trigonometric Function Programs

It appears that somewhere between the introduction
of the Wang 300-series calculators in 1965, and sometime in late 1968
to early 1969, Wang changed the design of the 300-series keyboard/display
units. The early keyboard/display units used a heavy metal casting
for the cabinet of the keyboard/display unit. Later, the design was
changed to use a cast high-density plastic cabinet.

300K/310K/320K Keyboard Circuit Board

The 300K, 310K, and 320K keyboard/display units all share the same
basic electronics, which consists of two circuit boards.
One of the circuit boards is the keyboard assembly. The keyboard circuit
board is identical between the 300, 310 and 320K keyboards, with the
difference being only the keys installed. The keyboard circuit boards are
populated with all of the necessary switches to provide the scientific
functions, but there are no keys installed on the 300K keyboard, and only
the square root and squaring function keys are installed on the 310K keyboard.

The keyboards of the 300-series Wang calculators
are a follow-on to the design of the Wang LOCI-2 keyboard. The keyboard
circuit board contains a number of micro-switches, as many as there are
keys on the keyboard. A special keystalk assembly causes the motion of
the depression of a key to press the actuator on the micro-switch, closing
the switch. The spring pressure of the micro-switch pushes the key back
up when released. This makes for very little key travel, perhaps 1/4-
inch at the most, but it is a very positive key actuation, with a nice 'click'
when the key is activated. The keycap legend is simply a printed piece of
card stock, that is retained under a clear plastic cover that snaps over
the top of the key.

A Side View of a Keyboard Assembly

The 300-series machines calculate to a full 14 digits of accuracy,
but only display 10 digits. This makes the machine quite accurate. Since
the Wang calculators used logarithms to perform multiplication and division,
and even though Dr. Wang's log-generating circuit produced very accurate
results, many logarithms are transcendental numbers which can never be
represented with 100% accuracy no matter how many digits they are calculated
out to. Because of the use of logarithms for multiplication and
division operations, the previous-generation
LOCI-2
could come up with results which would be slightly off. An example would be
multiplying 6 by 8. The LOCI-2 would give an answer of 47.99999999. While
47.99999999 is technically useful as a reasonably accurate answer, such a result
was generally considered 'incorrect' by most calculator users. To make
the 300-series more intuitive, these machines got the benefit of a special
circuit that provided a 'round off' function, which would cause such 6 x 8
to yield 48.0000000, which made the 300-series machine much more useful to
'non-technical' (such as business and financial) users. This round-off
function operated based on the non-displayed 11th digit (remember, the machines
calculate to 14 digits of accuracy internally) of results.

Display Circuit Board

The display circuit board is the same between all of the 300, 310, 320, and
360/362 keyboard/display units. The display is multiplexed, with the
decoding done on the circuit board by a series of diode/resistor gates
with transistor drivers. The display uses individual "Nixie"
(a name developed for the tubes by Burroughs, the company that invented
the display technology) tubes. The tubes used in the Wang 300-series
calculators were manufactured for Wang by National Electronics.

Nixie tubes display numbers by having ten different stacked electrodes which
are formed into the shape of digits, all packed into a little glass envelope
that looks like a small vacuum tube. The tube is filled with a mixture of
gases, consisting mostly of neon. When a given electrode is energized with
sufficient voltage (typically between 150 and 250 Volts DC), the gas around
the electrode ionizes, forming a glowing orange number. Nixie tubes were
commonly used in electronic equipment requiring numeric output through the
early '70's, when other less complex (and expensive) display technologies
displaced them.

All of the Nixie tubes in the Wang 300-series keyboard/display units
have pins (like old vacuum tubes) that plug into sockets on the display
driver circuit board. The digit display tubes have Wang part-number
340-0004, or National Electronics part-number NL-840. An special
eleventh Nixie tube, situated to the far left of the display, containing
only + and - (along with an 'upside down 8' that isn't used in the Wang
application), is used to indicate the sign of the number
in the display. This 'sign' tube has a Wang part number of 340-0005, or
National Electronics part number NL-843. Decimal points are indicated by
small discrete neon bulbs which are situated between the Nixie tubes.
The machine performs fully automatic decimal point placement, which was
a rare feature in early electronic calculators.

The Nixie Display in Operation

A Nixie Tube from a 300-Series Display

Overflows result in the overflow digits being discarded, and an 'overflow'
neon bulb at the far right end of the display that blinks when a detected
overflow condition occurs.

As mentioned above, there were two basic types of electronic packages
available, the "E", and the "SE" versions. The "S" stood for 'Simultaneous',
meaning that up to four keyboard/display units could be connected to the
electronics package, and operate as independent 'simultaneous' calculators.
The "SE" model machines add circuitry to the electronics package
to allow it to timeshare between each of the four keyboard/display units.
Timesharing between the keyboard/display units is done on a round-robin basis,
with each 'slice' of time ending when an operation is completed, i.e., if one
keyboard/display unit is performing a calculation, the others are
locked out until that operation completes, then the other units are given
their slice of time. Generally, this time-slicing is performed quickly
enough that it appears to each user as if they have their own dedicated
calculator.

The 360SE electronics package provides two add/subtract accumulators (called
the 'left' and 'right' accumulators, based on their keys location relative
to the numeric keypad on the keyboard), 4 memory store/recall registers,
multiply, divide, square root, x2, Loge(x),
and ex functions for each keyboard/display unit. It's up to
the keyboard/display unit to provide access to these functions.

The machine used a unique method of entry for problems. Add and subtract
operations are performed in postfix form, for example,

10 + 12 - 6 would be entered as: 10 + 12 + 6 -

Multiplication and division use an 'ENTER' key. For example,

10 X 12 / 16 would be entered as: 10 ENTER 12 X 16 /

Multiplication and division are performed using addition/subtraction of
logarithms. Entering a number, followed by the "ENTER" key causes
the Loge of that number to be calculated and placed in a hidden
register (not a stack, as in RPN-style calculators with ENTER keys). Entering
the next number, followed by either the multiply or divide key, causes
the loge of the entered number to be calculated, then the result
added (in the case of multiply) or subtracted (in the case of divide) to/from
the hidden register, then the antiloge of the result calculated,
and put into the display register.

The Model CP-1 Card Reader (First Design) and a Wang Punched Card

Second Design Model CP-1 Card Reader

Detail of a Wang Punch Card (part of the museum's collection)

Wang offered a number of peripheral devices for the 300-series
machines, including a punched card reader, Model CP-1, that used special
Wang-provided (but manufactured by IBM for Wang) cards that have die-cut
punch areas that can be manually punched out using a pencil point or other
pointed object. These cards are similar to the (in)famous "hanging chad"
punched cards used by Florida in the 2000 Presidential Election.

The "Port-a-Punch"Image Courtesy Michael Meyer

Wang sold an accessory (made
by IBM for Wang) called a "Port-O-Punch" that made punching cards easier,
providing a fixture for the card to set it, with a clear overlay that made
it more positive in terms of punching the card. The Port-O-Punch
provided a special stylus that also helped make it easier to punch
the cards accurately. Along with making the punching process easier,
the Port-O-Punch collects the 'punches' (called "chad") for easy disposal.

Each punched card card holds up to 80 steps.
The card reader is connected in series (daisy-chain) with a keyboard/display
unit.
Program instructions consist of a 6-bit code that corresponds
to a given key on the calculator keyboard. The card reader made simple
linear (no branching) programs possible.

The "Bed of Nails" Reading Method for the CP-1 Card Reader

The cards were read by a
'bed of nails' arrangement, with individual spring-loaded contacts
that would contact a set of fixed contacts on the other side of the
card. Two versions of the CP-1 were made, the earlier version
consisted of a hinged front cover which would unlatch to allow the
loading of a card. A later version replaced this design with a
lever-activated mechanism that opened a slot for the card to be inserted
in, then closed for reading. A later version of the card reader, called
the CP-2 added the ability for up to four
card readers to be daisy-chained together, allowing for larger (up to 320 step)
programs, and also added primitive unconditional branching and simple
conditional branches based on the sign of the number on the keyboard/display
unit the card reader(s) were connected to.

Wang 320K Keyboard with CP-1 Card Reader

Wang Labs maintained a large published library of programs for
applications in financial, statistics,
and engineering functions. Owners of Wang calculators could send away
for listings of programs for a wide range of applications. Users could
also submit their own programs to the program library for other users
to benefit from. Along with maintaining this library of programs, Wang
Labs published a monthly magazine entitled
"The Wang Laboratories Programmer"
that purchasers of Wang calculators automatically received a subscription to.
The magazine contained stories about the application of Wang calculators to a
wide range of disciplines, along with new product information, program library
information, and hints and tips for use of Wang's calculators.

The Model IC-1 Item Counter

Another interesting peripheral device was called the
"Item Counter", Model IC-1. This was an awkward
looking little box which connected to specially-modified keyboard/display
units. This device had an electromechanical counter in it, and a series
of switches that select functions on the keyboard unit.
Each time any of the selected key's functions (Add Left, Add Right, Subtract
Left, Subtract Right, Enter, Multiply, Square Root, or Square) on the
keyboard connected to the item counter is pressed, the counter advances
one count. This device would be useful for figuring averages or other
types of statistical and counting work.

In July of 1967, Wang introduced the Model 370
programming keyboard, which added higher-level programmability to the
300-series calculators. The 370 Programming Keyboard connected to
a Model 371 Card Reader (of slightly different design than the
CP-1 Card Programmer) allowing programs for
the 370 to be read from punched cards. The 370 added additional programming
operation codes to allow test and branch operations, capabilities that were
not possible with the CP-1 Card Programmer. The 370 Programming Keyboard
also included an I/O bus, allowing connection of a wide range of 37x-series
peripherals. Later, in March of 1968, Wang introduced the
Model 380 Programming Keyboard.
This device took the 370 to the next step, by providing true
learn mode programming. A built-in magnetic tape drive that accepted
a special 'tape loop' cassette provided the storage for programs. When the
380 was in learn mode, keypresses would be recorded onto the tape. To execute
a program, the tape would be 'played back'. The 380 was Wang's first
departure from their exclusive use of punched card programming.

The Wang Model 373 Data Storage Unit (Courtesy Michel Mollard)

Another particularly interesting peripheral device, introduced along
with the 370 programming keyboard, were the Model 372 and Model 373 data storage
units. These were rather large units, similar in size to the 300E-series
electronics package. The data storage unit provides 16 (Model 372) or 64
(Model 373) memory storage registers (organized logically as rows and columns
of numbers), and used core memory as the storage medium.
The data storage unit connects to the I/O bus of a Model 370 or Model 380
programming keyboard. The data storage unit was directed towards use in
solving array and matrix problems, such as calculating the solutions of
simultaneous linear equations.

Sincere thanks to Mr. Arnold Allen for donation of Wang 360SE Serial #380708 to the Old Calculator Museum